LiFePo Refit Part 23 AC

Hi Eric,

The advice I got from Fidel was specific to batteries mounted high in
the vertical fin.Â* Think of an inverted pendulum.Â* The visible damage
appears as long cracks in the gel coat partially around the tail boom at
the leading edge of the base of the fin.Â* I wouldn't be surprised that
there would be damage to the underlying structure, but I have no direct
knowledge of that.Â* I doubt there's any mechanical problem with fuselage
mounted batteries, though I always removed mine so that they'd be fully
charged when I arrived at my destination.Â* They were ease to remove,
however.

Dan

On 3/12/2020 8:43 AM, Eric Greenwell wrote:
wrote on 3/12/2020 1:35 AM:
I'll second the recommendation on batteries OUT for trailering.Â*
Especially tail fin installs.

Is that based on gel coat cracking (the original reason for removing
the tail battery), the potential for fires caused by the battery while
trailering, or to protect the battery from damage during trailering?

Removing the main batteries from a Schleicher motorglider (ASH 26E and
later), and DG motorgliders is very time-consuming. Since I'm not
aware of any problems caused by leaving the main batteries in during
trailering in these gliders, I think removing and replacing them is
likely to cause more problems than it avoids.


--
Dan, 5J

That's why when I replaced the SLA tail battery in my Experimental
LAK-17a with a LiFePO4, I placed the new battery behind the seat back.Â*
I replaced the weight removed from the tail with an ingot of lead of the
same weight as the battery that was removed.Â* The lead ingot was sealed
in the LAK removable battery box that was designed to fit that location.

On 3/12/2020 9:10 AM, Jonathon May wrote:
If you are changing from, SLA to lipo the distance from the Cof G is
important .
Just changing the nose battery in a ventus to lipo could make for a very
interesting day.


At 14:43 12 March 2020, Eric Greenwell wrote:
wrote on 3/12/2020 1:35 AM:
I'll second the recommendation on batteries OUT for trailering.
Especially tail fin installs.

Is that based on gel coat cracking (the original reason for removing the
tail
battery), the potential for fires caused by the battery while trailering,
or to
protect the battery from damage during trailering?

Removing the main batteries from a Schleicher motorglider (ASH 26E and
later), and
DG motorgliders is very time-consuming. Since I'm not aware of any
problems
caused
by leaving the main batteries in during trailering in these gliders, I
think
removing and replacing them is likely to cause more problems than it
avoids.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email
me)
- "A Guide to Self-Launching Sailplane Operation"

https://sites.google.com/site/motorg...ad-the-guide-1



--
Dan, 5J

The horizontal stabilizer on a glider weighs far more than any of the tail
batteries I've encountered, and when flying the glider, especially the takeoff and
landing, that heavy horizontal puts a lot more forces (vertically and twisting) on
the tail boom than the battery. In a trailer, the forces are almost entirely
vertical, and are also far less than the landing/takeoff pounding the tail gets.
So I'm skeptical the gel coat cracking is due to the battery during trailering.

How did Fidel determine it was the battery/trailering, and not the normal
operation of the glider, or some other cause?


Dan Marotta wrote on 3/12/2020 10:06 AM:
Hi Eric,

The advice I got from Fidel was specific to batteries mounted high in the vertical
fin.* Think of an inverted pendulum.* The visible damage appears as long cracks in
the gel coat partially around the tail boom at the leading edge of the base of the
fin.* I wouldn't be surprised that there would be damage to the underlying
structure, but I have no direct knowledge of that.* I doubt there's any mechanical
problem with fuselage mounted batteries, though I always removed mine so that
they'd be fully charged when I arrived at my destination.* They were ease to
remove, however.

Dan

On 3/12/2020 8:43 AM, Eric Greenwell wrote:
wrote on 3/12/2020 1:35 AM:
I'll second the recommendation on batteries OUT for trailering. Especially tail
fin installs.

Is that based on gel coat cracking (the original reason for removing the tail
battery), the potential for fires caused by the battery while trailering, or to
protect the battery from damage during trailering?

Removing the main batteries from a Schleicher motorglider (ASH 26E and later),
and DG motorgliders is very time-consuming. Since I'm not aware of any problems
caused by leaving the main batteries in during trailering in these gliders, I
think removing and replacing them is likely to cause more problems than it avoids.




--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

It's just a simple thing you can do to remove one risk factor.Â* Take it
for what it's worth and do what you like.

On 3/12/2020 12:09 PM, Eric Greenwell wrote:
The horizontal stabilizer on a glider weighs far more than any of the
tail batteries I've encountered, and when flying the glider,
especially the takeoff and landing, that heavy horizontal puts a lot
more forces (vertically and twisting) on the tail boom than the
battery. In a trailer, the forces are almost entirely vertical, and
are also far less than the landing/takeoff pounding the tail gets. So
I'm skeptical the gel coat cracking is due to the battery during
trailering.

How did Fidel determine it was the battery/trailering, and not the
normal operation of the glider, or some other cause?


Dan Marotta wrote on 3/12/2020 10:06 AM:
Hi Eric,

The advice I got from Fidel was specific to batteries mounted high in
the vertical fin.Â* Think of an inverted pendulum.Â* The visible damage
appears as long cracks in the gel coat partially around the tail boom
at the leading edge of the base of the fin.Â* I wouldn't be surprised
that there would be damage to the underlying structure, but I have no
direct knowledge of that.Â* I doubt there's any mechanical problem
with fuselage mounted batteries, though I always removed mine so that
they'd be fully charged when I arrived at my destination.Â* They were
ease to remove, however.

Dan

On 3/12/2020 8:43 AM, Eric Greenwell wrote:
wrote on 3/12/2020 1:35 AM:
I'll second the recommendation on batteries OUT for trailering.
Especially tail fin installs.

Is that based on gel coat cracking (the original reason for removing
the tail battery), the potential for fires caused by the battery
while trailering, or to protect the battery from damage during
trailering?

Removing the main batteries from a Schleicher motorglider (ASH 26E
and later), and DG motorgliders is very time-consuming. Since I'm
not aware of any problems caused by leaving the main batteries in
during trailering in these gliders, I think removing and replacing
them is likely to cause more problems than it avoids.





--
Dan, 5J

The loads and vibration imparted while trailering far exceed flight loads. Bob Carlton has trailered his airshow Salto around the country for years, and I can attest that a simple ten mile trip on the road will peg the G-Meter at +10 and -10 Gs. Side loads are probably not as severe, but we have no method of measuring those loads, simply because the Salto has a "V" tail, and the tail airfoils are removed for transport.

One thing I installed in my 1983 Cobra trailer is a thick foam pad at the top of the rudder box. When the trailer top is pulled down into the closed position, the foam compresses against the top of the rudder, damping side-to-side motion and vibration.

Still, it's a good idea to remove the top mounted tail battery. Gelcoat repairs aren't cheap, but fiberglass work is really expensive. Ask me how I know this.

wrote on 3/12/2020 6:26 PM:
The loads and vibration imparted while trailering far exceed flight loads. Bob Carlton has trailered his airshow Salto around the country for years, and I can attest that a simple ten mile trip on the road will peg the G-Meter at +10 and -10 Gs. Side loads are probably not as severe, but we have no method of measuring those loads, simply because the Salto has a "V" tail, and the tail airfoils are removed for transport.

One thing I installed in my 1983 Cobra trailer is a thick foam pad at the top of the rudder box. When the trailer top is pulled down into the closed position, the foam compresses against the top of the rudder, damping side-to-side motion and vibration.

Still, it's a good idea to remove the top mounted tail battery. Gelcoat repairs aren't cheap, but fiberglass work is really expensive. Ask me how I know this.

Typical mechanical G meters used in airplanes are very poor accelerometers. They
are underdamped, and respond to jostling by overshooting and oscillating. They do
a fine job measuring the much lower frequencies encountered during aerobatic
flight, but not the rattle and shake vehicle produces rolling down the road. Take
off from a bumpy grass strip, and you'll see the instrument peg itself.

In fact, measuring structural loads can be very complex. You can be certain that
10 g loads are not being transmitted from the tail battery to the tail boom, for
at least two reasons: the battery is not being subjected to 10 g loads, and the
frequencies of the loads that do exist are high enough that the loads are being
damped harmlessly by the intervening structure.

There is a good reason that none of the manufacturers require the tail battery to
be removed during trailering: it does no harm. Anyone concerned about the safety
of leaving the battery in the tail should contact their glider's manufacturer for
the correct procedures.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

Mark, if you're really interested you could rotate the G-meter 90
degrees in either direction. :-D

On 3/12/2020 7:26 PM, wrote:
The loads and vibration imparted while trailering far exceed flight loads. Bob Carlton has trailered his airshow Salto around the country for years, and I can attest that a simple ten mile trip on the road will peg the G-Meter at +10 and -10 Gs. Side loads are probably not as severe, but we have no method of measuring those loads, simply because the Salto has a "V" tail, and the tail airfoils are removed for transport.

One thing I installed in my 1983 Cobra trailer is a thick foam pad at the top of the rudder box. When the trailer top is pulled down into the closed position, the foam compresses against the top of the rudder, damping side-to-side motion and vibration.

Still, it's a good idea to remove the top mounted tail battery. Gelcoat repairs aren't cheap, but fiberglass work is really expensive. Ask me how I know this.

--
Dan, 5J